TYPES OF LEVERS There are three types or classes of levers, according to where the load and effort are located with respect to the fulcrum.

FIRST CLASS LEVER

First-class levers have the fulcrum placed between the load and the effort, as in the seesaw, crowbar, and balance scale. If the two arms of the lever are of equal length, as with the balance scale, the effort must be equal to the load. If the effort arm is longer than the load arm, as in the crowbar, the effort travels farther than the load and is less than the load.

Second-class levers have the load between the effort and the fulcrum. A wheelbarrow is a second-class lever. The wheel’s axle is the fulcrum, the handles take the effort, and the load is placed between them. The effort always travels a greater distance and is less than the load.

Third-class levers have the effort placed between the load and the fulcrum. The effort always travels a shorter distance and must be greater than the load. A hammer acts as a third- class lever when it is used to drive in a nail: the fulcrum is the wrist, the effort is applied through the hand, and the load is the resistance of the wood. Another example of a third-class lever is the human forearm: the fulcrum is the elbow, the effort is applied by the biceps muscle, and the load is in the hand.

3 TYPES OF PULLEYS There are three main types of pulleys: fixed, movable, and compound..

A fixed pulley describes a pulley that is secured to a single spot. While the pulley's wheel will turn with the rope or chord that passes through it, the pulley itself will remain stationary. Because of this, the force exerted on the object on the opposite side of the pulley will be exactly the amount of force applied on the user's side of the pulley. This is described as having a mechanical advantage of one, because the amount of force you apply is precisely the amount of force the machine will exert on the object you are trying to move.

Movable Pulley - A movable pulley is a pulley that moves with the load you are moving, as opposed to a fixed pulley which does not move. However, unlike the fixed pulley which exerts only as much force on the object being moved as is applied to the machine, a movable pulley will multiple the force which the user applies to the machine in doing work on an object. This means that less force must be applied by the user to do the same amount of work, effectively making the work what might be described as "easier."

A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads.pulleysropecable The pulleys are assembled together to form blocks and then blocks are paired so that one is fixed and one moves with the load. The rope is threaded, or rove, through the pulleys to provide mechanical advantage that amplifies that force applied to the rope.blocksmechanical advantage